Secondary battery system

Abstract

To suppress a spreading fire from a firing battery to the other battery while suppressing performance reduction of a secondary battery.SOLUTION: A secondary battery system comprises: a secondary battery; a housing part in which the secondary battery is stored and which is filled with an oxygen-free medium; and a cooling part which is disposed inside of the housing part and cools the secondary battery via the medium. The secondary battery includes a safety valve which releases a pressure inside of the secondary battery when the pressure inside of the secondary battery reaches a predetermined pressure value, and the safety valve is disposed at a position opposed to the cooling part via the medium.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a secondary battery system. [Background technology]

[0002] Secondary batteries used as batteries for electric vehicles and the like are known (see, for example, Patent Document 1). In the secondary battery described in Patent Document 1, each of a plurality of battery modules (batteries) is connected to a heat sink via a heat pipe. A cooling water passage is formed in the heat sink, through which coolant cooled by a radiator flows. Therefore, the secondary battery, which heats up during charging and discharging, is cooled by the heat sink through which coolant flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-204151 Summary of the Invention [Problem to be solved by the invention]

[0004] In secondary batteries in which multiple batteries are stacked, the temperature of the battery may rise due to external short circuits caused by external stress such as collisions when the battery is loaded onto a vehicle, initial contamination of the electrodes and electrolyte with impurities, internal short circuits between electrodes caused by battery deterioration, or insufficient cooling capacity during high-speed charging and discharging. If the temperature of the battery reaches the ignition temperature of the battery material, the battery may ignite. At this time, the heat generation triggers a decomposition reaction of the negative electrode SEI film (Solid Electrolyte Interface) and an exothermic reaction between the negative electrode and the electrolyte. If the separator melts down due to the exothermic reaction, the entire surface of the electrode is short-circuited. The heat generation and temperature rise of the battery cause an exothermic reaction between the positive electrode and the electrolyte and a decomposition reaction of the electrolyte, and the temperature of the ignited battery rises rapidly. If one battery ignites when multiple batteries are stacked, the temperature of the adjacent batteries may reach the ignition temperature due to heat conduction from the ignited battery through the tube walls, etc., and ignite, and then multiple batteries may ignite in sequence (battery fire). Although the spreading of fire among batteries can be suppressed to some extent by disposing a heat insulating material between each of the multiple batteries, there are problems such as an increase in cost due to the heat insulating material and a decrease in volumetric efficiency according to the volume of the heat insulating material. Even if the heat insulating material is disposed between the batteries, the spreading of fire among the batteries may occur due to heat transfer via the heat sink. In this regard, Patent Document 1 does not take into consideration the spreading of fire among other batteries caused by one igniting battery.

[0005] The present invention has been made to solve at least some of the above-mentioned problems, and aims to prevent a fire from spreading from a igniting battery to other batteries while suppressing deterioration in performance of the secondary battery. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0007] (1) According to one aspect of the present invention, there is provided a secondary battery system comprising: a secondary battery, a housing portion that houses the secondary battery and is filled with an oxygen-free medium, and a cooling portion that is disposed inside the housing portion and cools the secondary battery via the medium, the secondary battery having a safety valve that releases pressure inside the secondary battery when the pressure inside the secondary battery reaches a predetermined pressure value, and the safety valve is disposed in a position facing the cooling portion via the medium.

[0008] According to this configuration, when the pressure inside the secondary battery, which has ignited due to a rise in temperature, rises and reaches a predetermined pressure value, components such as the electrolyte of the secondary battery are released into the housing through the open safety valve. In this case, a part of the main components of the liquid released from the high-pressure secondary battery into the low-pressure housing evaporates. Meanwhile, the remaining main components of the liquid are released into the housing as liquid. Since the gas released from the secondary battery contains decomposition oxygen of the secondary battery, when the safety valve is opened, a combustion flame generated by the decomposition oxygen and combustible components in the secondary battery flows into the housing. However, in this configuration, the housing is filled with a medium that does not contain oxygen. Therefore, oxygen in the housing in the atmosphere after the safety valve is opened is blocked, and diffusion combustion caused by the combustible components in the premixed gas and the oxygen components in the atmosphere that occurs when the safety valve is opened in an atmospheric atmosphere is suppressed. Furthermore, since the vapor pressure of the electrolyte components released into the housing is low, the electrolyte components in the gas released from the secondary battery into the housing remain in the housing as liquid without vaporizing. In addition, since the safety valve is disposed in a position facing the cooling part, the cooling part acts as a cooling surface when the gas discharged from the safety valve impinges on the gas. Therefore, the combustion flame is extinguished by the heat loss effect caused by the strong temperature gradient between the safety valve and the cooling part. As a result, for example, there is no need to provide a heat insulating material or the like to suppress the spread of fire, and the performance degradation of the secondary battery is suppressed, and the spread of fire from a ignited secondary battery to other secondary batteries is suppressed.

[0009] (2) In the secondary battery system of the above aspect, the distance between the safety valve and the cooling part may be set to be equal to or shorter than a quenching distance. According to this configuration, the distance between the cooling section and the safety valve disposed opposite the cooling section is equal to or less than the quenching distance, so that the combustion flame that flows from inside the secondary battery into the housing section is quenched by the large temperature gradient with the wall surface of the cooling section, causing the flame to be extinguished.

[0010] (3) The secondary battery system of the above aspect may further include a temperature acquisition unit that acquires a battery temperature, which is the temperature of the secondary battery, and a control unit that uses the battery temperature to control the temperature and pressure of the medium, wherein the medium is a fluorocarbon-based medium, the cooling unit is disposed vertically above the secondary battery, and the control unit may control the temperature of the fluorocarbon-based medium to adjust the temperature of the secondary battery using the heat of evaporation of the fluorocarbon-based medium and to change the vapor pressure of the fluorocarbon-based medium. According to this configuration, the medium filled in the storage section is a fluorocarbon-based medium having a low boiling point. During charging and discharging when the secondary battery is not ignited, the temperature during charging and discharging and the boiling point are adjusted to efficiently cool the secondary battery by utilizing the latent heat of vaporization of the fluorocarbon-based medium. Furthermore, ignition of the secondary battery is detected based on the battery temperature acquired by the temperature acquisition section. In the event that the secondary battery ignites, the temperature of the fluorocarbon-based medium is made even lower than when the secondary battery is charged and discharged, thereby cooling the ignited secondary battery and suppressing the spread of fire between the secondary batteries.

[0011] (4) In the secondary battery system of the above aspect, the cooling unit has a refrigerant flow path through which a refrigerant flows, and the secondary battery system further includes a first thermal expansion valve that expands the refrigerant due to a pressure difference between its upstream and downstream sides, and a second thermal expansion valve that expands the refrigerant due to a pressure difference between its upstream and downstream sides that is greater than the pressure difference of the first thermal expansion valve, and the control unit may supply the refrigerant to the secondary battery via the first thermal expansion valve when the battery temperature is lower than a first temperature, and supply the refrigerant to the secondary battery via the second thermal expansion valve when the battery temperature is equal to or higher than the first temperature. According to this configuration, the refrigerant is supplied to the refrigerant flow path via the first thermal expansion valve when the secondary battery is charged or discharged, and the refrigerant is supplied to the refrigerant flow path via the second thermal expansion valve when the secondary battery catches fire. As a result, when the secondary battery catches fire, the refrigerant that has expanded further due to the pressure difference and has a lower temperature than the first thermal expansion valve is supplied to the refrigerant flow path via the second thermal expansion valve. As a result, a refrigerant with a lower temperature than when the secondary battery is not caught is supplied to the storage section that contains the ignited secondary battery, and the ignited secondary battery is cooled.

[0012] (5) The secondary battery system of the above aspect may further include a heat transfer layer made of metal, connected to a surface of the secondary battery, and connected to the refrigerant flow path; and a porous body connected to the secondary battery via the heat transfer layer and formed of a porous material. According to this configuration, the liquid fluorocarbon medium cooled by the refrigerant flowing through the refrigerant flow path spreads quickly throughout the porous body due to the capillary phenomenon caused by the porous body connected to the refrigerant flow path. The liquid fluorocarbon medium in the porous body exchanges heat with the secondary battery through the heat transfer layer in contact with the porous body. The fluorocarbon medium that has changed from liquid to gas due to the heat exchange moves above the secondary battery where the refrigerant flow path is arranged, is cooled and changes to liquid, and cools the secondary battery again. That is, according to this configuration, the secondary battery is quickly cooled by the vapor heat transport of the fluorocarbon medium using the capillary phenomenon of the porous body. On the other hand, if the secondary battery ignites and is at a high temperature, the fluorocarbon medium cannot condense in time and dry out occurs around the ignited secondary battery. When dry out occurs, heat is transferred from the ignited secondary battery to the adjacent secondary battery by thermal radiation from the heat transfer layer. In this configuration, the heat transfer layer is connected to the refrigerant flow path, so that the secondary battery is quickly cooled, and heat transfer between the secondary batteries due to thermal radiation is suppressed.

[0013] (6) The secondary battery system of the above aspect may further include a tank storing an antifreeze liquid having electrical insulation, and an on-off valve that opens and closes the connection between the storage unit and the outside, and when the battery temperature changes from below a second temperature to above the second temperature, the control unit may release the fluorocarbon-based medium from inside the storage unit by opening the on-off valve, and supply antifreeze liquid from the tank to the inside of the storage unit after the fluorocarbon-based medium has been released. According to this configuration, when the secondary battery changes from a state below the second temperature where it has not ignited to a state equal to or higher than the second temperature where it has ignited, the container is filled with the supplied antifreeze liquid. Covering the secondary battery with antifreeze liquid suppresses contact between the ignited secondary battery and oxygen, and the temperature of the secondary battery is managed by controlling the temperature of the antifreeze liquid. In particular, when there is a secondary battery that has not completely burned, re-ignition of the secondary battery that has not completely burned after several hours or days is suppressed by filling the container with antifreeze liquid.

[0014] (7) The secondary battery system of the above aspect may further include a first pressure regulating valve that releases the pressure inside the storage unit, and a second pressure regulating valve connected in series between the storage unit and the first pressure regulating valve, wherein the first pressure regulating valve opens when the pressure inside the storage unit reaches a first pressure value and maintains the open state, and the second pressure regulating valve opens when the pressure inside the storage unit is equal to or greater than a second pressure value that is smaller than the first pressure value and greater than atmospheric pressure, and closes when the pressure is less than the second pressure value. According to this configuration, a second regulating valve that opens and closes at a low second pressure value on the upstream side of the storage unit, and a first regulating valve that opens at a high first pressure value and is fixed in an open state on the downstream side of the second regulating valve are connected to the storage unit. When the secondary battery is charging and discharging without ignition, the fluorocarbon medium in the storage unit cools the secondary battery at a pressure equal to or greater than the second pressure value and less than the first pressure value. In this case, since the second regulating valve is open and the first regulating valve is closed, the fluorocarbon medium in the storage unit is not released to the atmosphere. On the other hand, when the secondary battery ignites and the pressure in the storage unit changes to the first pressure value or more, the first regulating valve is also opened in addition to the second regulating valve. In this case, the fluorocarbon medium in the storage unit is released to the atmosphere and the pressure in the storage unit decreases. As a result, damage to the container such as the storage unit due to an increase in pressure in the storage unit can be suppressed. In addition, if the pressure in the storage unit decreases and changes to less than the second pressure value after the first regulating valve is opened, the second regulating valve is closed. Since the second pressure value is set higher than atmospheric pressure, even if the pressure inside the storage unit drops, air containing oxygen does not flow from the atmosphere into the storage unit. In other words, according to this configuration, the pressure increase when the secondary battery ignites is suppressed, thereby suppressing damage to the container such as the storage unit and suppressing the progression of ignition due to the flow of oxygen from the atmosphere into the storage unit.

[0015] The present invention can be realized in various forms, for example, in the form of a secondary battery, a lithium ion battery, a secondary battery system, a control method for a secondary battery, a system including these devices or implementing these methods, a computer program for executing these devices or methods, a server device for distributing this computer program, a non-transitory storage medium on which a computer program is stored, etc. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic perspective view of a secondary battery system according to an embodiment of the present invention; [Diagram 2] 2 is a schematic cross-sectional view of a portion of the secondary battery system. [Diagram 3]FIG. 11 is a schematic block diagram of a secondary battery system according to a second embodiment in a state in which a first thermal expansion valve is connected to an external flow path. [Figure 4] FIG. 11 is a schematic block diagram of a secondary battery system according to a second embodiment in a state in which a second thermal expansion valve is connected to an external flow path. [Diagram 5] 13 is an example of a Ph diagram of a vapor compression refrigeration cycle in a second embodiment. [Figure 6] 6 is a schematic cross-sectional view of a portion of a secondary battery system according to a second embodiment. FIG. [Figure 7] FIG. 11 is an explanatory diagram of the positions at which the temperatures of eight battery cells arranged in the storage section are detected. [Figure 8] FIG. 13 is an explanatory diagram of the temperature changes in each of six battery cells when one battery cell catches fire. [Figure 9] FIG. 13 is an explanatory diagram of measurement positions of heat flux of eight battery cells arranged in a storage section. [Figure 10] FIG. 2 is an explanatory diagram of the change in heat flux over time during radiation. [Figure 11] FIG. 13 is an explanatory diagram of the change in heat flux over time in the heat flow direction of a heat transfer layer. [Figure 12] FIG. 11 is an explanatory diagram of temperature changes in each of eight battery cells in a secondary battery system that does not include a second thermal expansion valve. [Figure 13] FIG. 11 is an explanatory diagram of the change over time in heat flux during radiation in a secondary battery system not including a second thermal expansion valve. [Figure 14] FIG. 11 is a schematic block diagram of a secondary battery system according to a third embodiment when charging and discharging a battery cell. [Figure 15] FIG. 11 is a schematic block diagram of a secondary battery system according to a third embodiment after a battery cell ignites. [Figure 16] FIG. 11 is a schematic block diagram of a secondary battery system according to a fourth embodiment. [Figure 17] FIG. 13 is a schematic block diagram of a secondary battery system according to a fifth embodiment. [Figure 18] 4 is a schematic diagram of a container removed from the secondary battery system. FIG. [Figure 19]1 is a schematic diagram of a container connected to a cooling circulation system different from the secondary battery system. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] First Embodiment FIG. 1 is a schematic perspective view of a secondary battery system 100 according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a portion of the secondary battery system 100. The secondary battery system 100 shown in FIG. 1 includes a plurality of battery cells (secondary batteries) 20, a storage section 10 that stores the plurality of battery cells 20, and a refrigerant flow path 30 disposed in the storage section 10. The storage section 10 is filled with a medium 15 that does not contain oxygen. As shown in FIG. 2, the battery cell 20A includes a safety valve 21A that releases pressure in the battery cell 20A. The safety valve 21A is disposed at a position facing the refrigerant flow path 30 via the medium 15. In this embodiment, when the battery cell 20A ignites and the pressure in the battery cell 20A reaches a predetermined pressure value, the safety valve 21A opens and the pressure in the battery cell 20A is released. Since the storage section 10 is filled with the medium 15 that does not contain oxygen, the ignition of the battery cell 20A is extinguished. Furthermore, because the safety valve 21A is disposed at a position facing the coolant flow path 30, gas and the like released from within the battery cell 20A is quickly cooled.

[0018] As shown in FIG. 1, the battery cells 20 are arranged side by side along the X-axis parallel to the horizontal direction so as not to contact each other. The battery cells 20 of this embodiment are lithium ion batteries having an approximately rectangular parallelepiped shape. Each of the battery cells 20 is the same battery cell. In the battery cells 20, components such as an electrolyte and electrodes are sealed in a housing that forms an outer frame. The storage section 10 has an approximately rectangular parallelepiped box shape. In FIG. 1, the outline of the storage section 10 is shown by a dashed line. Also, FIG. 1 shows an orthogonal coordinate system CS. The orthogonal coordinate system CS is composed of an X-axis, a Y-axis, and a Z-axis that are parallel to each side of the storage section 10 having an approximately rectangular parallelepiped shape and are orthogonal to each other. The orthogonal coordinate system CS shown in FIG. 1 corresponds to the orthogonal coordinate system CS shown in FIG. 2 and subsequent figures.

[0019] As shown in FIG. 1, the battery cell 20 has a substantially rectangular parallelepiped shape extending along the Y axis. Since the storage section 10 is filled with the medium 15, the multiple battery cells 20 can be said to be stacked along the X axis direction via the medium 15. In the storage section 10, a refrigerant flow path 30 through which a refrigerant 32 flows is formed vertically above the multiple battery cells 20. As shown in FIG. 1, the refrigerant flow path 30 has a bottom surface parallel to the XY plane and has a substantially rectangular parallelepiped shape with a thickness along the vertical direction (Z axis direction). Since a space is formed inside the substantially rectangular parallelepiped shape, the refrigerant 32 flows inside the refrigerant flow path 30. The refrigerant flow path 30 is connected to a cylindrical external flow path 35 extending from the outside of the storage section 10. The refrigerant 32 that has dissipated heat by a heat sink such as a radiator not shown in FIG. 1 circulates in the direction of the arrow and flows into the refrigerant flow path 30 via the external flow path 35. The coolant flow passage 30 and the multiple battery cells 20 are not in direct contact with each other, but are indirectly connected via the medium 15. In this embodiment, water is used as the coolant 32.

[0020] Fig. 2 shows a schematic cross-sectional view parallel to the ZX plane of two battery cells 20A, 20B among the multiple battery cells 20. As shown in Fig. 2, the battery cells 20A, 20B are provided with safety valves 21A, 21B at positions facing the refrigerant flow path 30 arranged vertically above. The safety valves 21A, 21B of this embodiment open when the pressure reaches a predetermined pressure value, thereby releasing the pressure inside the battery cells 20A, 20B.

[0021] 2, the refrigerant flow path 30 includes a pipe wall 31 that forms a flow path through which the refrigerant 32 flows. The secondary battery system 100 includes a heat transfer member 50 that extends vertically, is connected to the pipe wall 31 of the refrigerant flow path 30, and is formed on the surface of each of the battery cells 20A, 20B. The heat transfer member 50 is made of a metal with high thermal conductivity. The battery cells 20A, 20B are cooled by exchanging heat with the refrigerant flow path 30 and the medium 15 via the heat transfer member 50.

[0022] 2 shows a state in which one of the battery cells 20A has ignited and the safety valve 21A has been opened. The opened safety valve 21A is indicated by a dashed line. Here, the battery cell 20A and the refrigerant flow path 30 are arranged in the accommodation section 10 so that the distance L0 between the safety valve 21A and the refrigerant flow path 30 is equal to or less than the quenching distance. The quenching distance is calculated using the dimensionless Peclet number Pe, which is the ratio between the heat generation rate Qp and the heat loss rate Qd due to flame propagation. For example, the quenching distance of propane flame propagation is set so that the Peclet number Pe is 8 or less.

[0023] Here, the heat release rate Qp(W) due to flame propagation is expressed by the following formula (1).

number

[0024] The heat loss rate Qd used in the Peclet number Pe is expressed by the following equation (2).

number

[0025] 1 is set to be equal to or less than the quenching distance. As a result, even if a premixed flame caused by premixed combustion in the battery cell 20A occurs in the accommodation section 10, the heat loss rate Qd exceeds the heat generation rate Qp, so that the premixed flame is extinguished and combustion in the accommodation section 10 is suppressed.

[0026] When premixed combustion in the storage unit 10 is suppressed, the electrolyte component 22 (FIG. 2) in the gas released from the battery cell 20A changes from high pressure in the battery cell 20A to low pressure in the storage unit 10. Therefore, the electrolyte component 22 is difficult to volatilize (evaporate) due to its low vapor pressure, and accumulates as liquid droplets vertically downward in the storage unit 10. The unburned electrolyte component 22 accumulated in the storage unit 10 is collected after cooling.

[0027] As described above, the secondary battery system 100 of this embodiment includes the battery cell 20, the storage section 10 that stores the battery cell 20, and the refrigerant flow path 30 disposed in the storage section 10, as shown in FIG. 1. The storage section 10 is filled with a medium 15 that does not contain oxygen. Also, as shown in FIG. 2, the battery cell 20A includes a safety valve 21A that releases the pressure in the battery cell 20A when the pressure in the battery cell 20A reaches a predetermined pressure value. The safety valve 21A is disposed at a position facing the refrigerant flow path 30 via the medium 15. In this embodiment, when the pressure in the battery cell 20A that has ignited due to a rise in temperature rises and reaches a predetermined pressure value, the electrolyte component 22 (e.g., ethylene carbonate, ethyl methyl carbonate, DMC dimethyl carbonate) in the battery cell 20A is released into the storage section 10 through the opened safety valve 21A. In this case, a part of the electrolyte component 22 released from the high-pressure battery cell 20A into the low-pressure storage section 10 evaporates. On the other hand, the remaining electrolyte component 22 is released as a liquid into the storage section 10. Since the gas released from the battery cell 20A contains oxygen from the decomposition of the battery cell 20A, when the safety valve 21A is opened, a combustion flame generated by premixed combustion of the decomposition oxygen and the combustible components in the battery cell 20A flows into the storage section 10. However, in this embodiment, the storage section 10 is filled with a medium that does not contain oxygen. Therefore, oxygen in the storage section 10 in the atmosphere after the safety valve 21A is opened is blocked, and diffusion combustion caused by the combustible components in the premixed gas and the oxygen components in the atmosphere that occurs when the safety valve is opened in the atmospheric atmosphere is suppressed. Furthermore, since the vapor pressure of the electrolyte component 22 is low, the electrolyte component 22 in the gas released from the battery cell 20A into the storage section 10 remains in the storage section 10 as a liquid without being vaporized. In addition, since the safety valve 21A is arranged at a position facing the refrigerant flow path 30, the refrigerant flow path 30 acts as a cooling surface when the gas released from the safety valve 21A impinges on the gas. Therefore, the premixed combustion flame in the battery cell 20A is extinguished by the heat loss effect caused by the strong temperature gradient between the safety valve 21A and the refrigerant flow path 30. As a result, the space filled with the medium 15 functioning as a thermal insulator, which is disposed between the battery cell 20A and the battery cell 20B, does not need to be larger than necessary.Therefore, in this embodiment, the performance degradation of the multiple battery cells 20 is suppressed, and the spread of fire from a ignited battery cell 20A to other battery cells 20B is also suppressed.

[0028] 2, the battery cell 20A and the refrigerant flow path 30 are arranged in the housing 10 so that the distance L0 between the safety valve 21A of the battery cell 20A and the refrigerant flow path 30 is equal to or less than the quenching distance. With this configuration, the distance between the refrigerant flow path and the safety valve arranged at a position facing the refrigerant flow path is equal to or less than the quenching distance. Therefore, the combustion flame that flows from inside the secondary battery into the housing 10 outside the secondary battery is extinguished by a quenching phenomenon caused by a large temperature gradient with the wall surface of the refrigerant flow path.

[0029] <Second embodiment> 3 is a schematic block diagram of a secondary battery system 100a of the second embodiment. The second embodiment is significantly different from the first embodiment in that a thermal expansion valve that thermally expands a refrigerant 32a is switched when a battery cell 20A ignites, and that the battery cell 20 is cooled by vapor heat transport using a medium 15a that is a fluorocarbon-based medium with a low boiling point (for example, 20 degrees Celsius (°C) at atmospheric pressure).

[0030] The secondary battery system 100a of the second embodiment is a secondary battery system mounted on a vehicle. As shown in Fig. 3, the secondary battery system 100a of the second embodiment includes a storage section 10a that stores a plurality of battery cells 20 and is filled with a medium 15a, a refrigerant flow path 30a arranged vertically upward in the storage section 10a, an external flow path 35 connected to the refrigerant flow path 30a, a compressor 60 arranged on the external flow path 35, a condenser 70, a first thermal expansion valve 81, a second thermal expansion valve 82, a temperature sensor (temperature acquisition section) S1 that detects the temperature (battery temperature) of the battery cell 20A, a low-pressure regulating valve 90, and a control section 40.

[0031] 3, a compressor 60, a condenser 70, a first thermal expansion valve 81, and a second thermal expansion valve 82 are arranged in this order from the upstream side on the external flow path 35 along the flow of the refrigerant 32a flowing in the refrigerant flow path 30a. The refrigerant 32a in the second embodiment is a fluorocarbon medium (e.g., R134a, R1234yf, which have a boiling point of −29° C. at atmospheric pressure) used in car air conditioners, a household refrigerant, a natural refrigerant (only non-flammable CO2), or the like. The refrigerant flow path 30a may be used as a heat exchanger, and the refrigerant may be configured to flow into the refrigerant flow path 30a after heat exchange with an antifreeze such as LLC (Long Life Coolant), which does not freeze even at 0° C. or lower (e.g., −30° C.) at atmospheric pressure (not shown).

[0032] The first thermal expansion valve 81 and the second thermal expansion valve 82 are arranged in parallel with respect to the external flow path 35. Only one of the first thermal expansion valve 81 and the second thermal expansion valve 82 is connected to the external flow path 35 under the control of the control unit 40. In other words, the refrigerant 32a circulates through the inside of the accommodating unit 10, the compressor 60, the condenser 70, and the first thermal expansion valve 81 or the second thermal expansion valve 82 via the refrigerant flow path 30a and the external flow path 35.

[0033] The compressor 60 is a compressor that compresses the refrigerant 32a flowing through the external flow path 35. The condenser 70 is a radiator mounted on a vehicle that dissipates heat of the compressed refrigerant 32a to the outside. The first thermal expansion valve 81 and the second thermal expansion valve 82 expand the refrigerant 32a flowing through the external flow path 35 by the pressure difference between the upstream side and the downstream side of the first thermal expansion valve 81 and the second thermal expansion valve 82. When the refrigerant 32a expands by the first thermal expansion valve 81 or the second thermal expansion valve 82, the temperature of the refrigerant decreases. The second thermal expansion valve 82 has a larger pressure difference than the first thermal expansion valve 81. Therefore, the temperature of the refrigerant 32a expanded by the second thermal expansion valve 82 is further decreased than the temperature of the refrigerant 32a expanded by the first thermal expansion valve 81. Note that FIG. 3 shows a state in which the first thermal expansion valve 81 is connected to the external flow path 35. The external flow path 35 connecting the second thermal expansion valve 82 that is not connected to the external flow path 35 is shown by a dashed line.

[0034] The low-pressure regulating valve 90 is a valve that releases the medium 15a in the storage section 10a to the outside when any of the battery cells 20 ignites and the pressure in the storage section 10a increases. The gauge pressure of the low-pressure regulating valve 90 is set to atmospheric pressure or a pressure higher than atmospheric pressure. The opening and closing of the low-pressure regulating valve 90 is controlled by a control signal from the control section 40. The control section 40 opens the low-pressure regulating valve 90 when any of the battery cells 20 ignites, and keeps the low-pressure regulating valve 90 closed when none of the battery cells 20 have ignited. Note that FIG. 3 shows a state in which none of the battery cells 20 have ignited and the low-pressure regulating valve 90 is closed.

[0035] The control unit 40 controls the temperature of the refrigerant 32a supplied to the refrigerant flow path 30a in the storage unit 10a using the temperature detected by the temperature sensor S1, thereby controlling the temperature of the medium 15a filled in the storage unit 10a. By controlling the temperature of the medium 15a, the control unit 40 adjusts the temperature of the multiple battery cells 20 using the heat of evaporation of the medium 15a, which is a fluorocarbon medium having a low boiling point, and changes the vapor pressure of the medium 15a.

[0036] When the temperature detected by the temperature sensor S1 is less than the threshold value of 80°C (first temperature), the control unit 40 determines that none of the battery cells 20 have ignited. In this case, the control unit 40 connects the external flow path 35 to the first thermal expansion valve 81 as a charging / discharging time when the battery cells 20 have not ignited as shown in FIG. 3. The control unit 40 supplies the refrigerant 32a cooled to 20°C via the first thermal expansion valve 81 to the refrigerant flow path 30a in the storage unit 10a. As an example, in the second embodiment, when the temperature of the battery cells 20 during charging / discharging is 25°C, the battery cells 20 are cooled by the refrigerant 32a whose temperature has been reduced to 0.6 MPa and 20°C by the first thermal expansion valve 81. Meanwhile, the refrigerant 32a discharged from the refrigerant flow path 30a in the storage unit 10a is compressed to 50°C by the compressor 60. The refrigerant 32a whose temperature has been increased by the compressor 60 has its heat dissipated to the outside by the condenser 70 and is expanded again by the first thermal expansion valve 81.

[0037] FIG. 4 is a schematic block diagram of the secondary battery system 100a of the second embodiment in a state in which the second thermal expansion valve 82 is connected to the external flow path 35. FIG. 4 shows a schematic block diagram of the secondary battery system 100a in a case in which one of the multiple battery cells 20 ignites and the connection destination of the external flow path 35 is changed from the first thermal expansion valve 81 to the second thermal expansion valve 82. When the temperature detected by the temperature sensor S1 reaches 80° C., the control unit 40 determines that one of the battery cells 20 has ignited. In this case, the control unit 40 supplies the refrigerant 32a to the refrigerant flow path 30a in the storage unit 10a via the second thermal expansion valve 82 instead of the first thermal expansion valve 81. In addition, the control unit 40 opens the low-pressure regulating valve 90 that was closed. When the low-pressure regulating valve 90 opens, the medium 15a in the storage unit 10a is released to the atmosphere, and the pressure in the storage unit 10a decreases.

[0038] 4 as an example, in the state of the second embodiment, when the battery cell 20 ignites and its temperature becomes 80°C or higher, the battery cell 20 is cooled by the refrigerant 32a whose temperature has been reduced to -29°C by the second thermal expansion valve 82. Meanwhile, the refrigerant 32a discharged from the refrigerant flow path 30a in the housing portion 10a is compressed to 50°C by the compressor 60, and then heat is dissipated by the condenser 70, in the same manner as during charging and discharging of the battery cell 20 shown in FIG.

[0039] Fig. 5 is an example of a Ph diagram of a vapor compression refrigeration cycle in the second embodiment. As shown in Fig. 5, during charging and discharging of the battery cell 20 shown in Fig. 3, the first thermal expansion valve 81 causes the refrigerant 32a to expand to 0.6 MPa and 20°C. On the other hand, during ignition of the battery cell 20 shown in Fig. 4, the second thermal expansion valve 82 causes the refrigerant 32a to expand to approximately 0.08 MPa and -29°C. In the second embodiment, as shown in Fig. 5, the workload of the compressor 60 during ignition in Fig. 4 is set to three times the workload of the compressor 60 during charging and discharging in Fig. 3.

[0040] Fig. 6 is a schematic cross-sectional view of a portion of a secondary battery system 100a of the second embodiment. Fig. 6 shows a schematic cross-sectional view parallel to the ZX plane of two battery cells 20A and 20B among the multiple battery cells 20, as in Fig. 2 of the first embodiment. Unlike the first embodiment, the heat transfer member 50a of the second embodiment includes a heat transfer layer 51 formed in direct contact with the surfaces of the battery cells 20A and 20B, and a porous body 52 formed of a porous material on the surface of the heat transfer layer 51.

[0041] The heat transfer layer 51 and the porous body 52 extend in a vertical direction perpendicular to the stacking direction of the multiple battery cells 20A, 20B, and are connected to the pipe wall 31 of the refrigerant flow path 30a. The heat transfer layer 51 is made of the same metal with high thermal conductivity as the heat transfer member 50 of the first embodiment. The porous body 52 is formed on the surface of the heat transfer layer 51 that is formed on the surface of the battery cells 20A, 20B, without being in direct contact with the battery cells 20A, 20B. The porous body 52 is made of aluminum with a porosity of 80%, an opening of 100 μm, and a thickness of 0.5 mm.

[0042] Fig. 6 shows a state in which the battery cells 20A, 20B are being charged and discharged without catching fire. When the battery cells 20A, 20B are being charged and discharged, as shown in Fig. 6, the medium 15a that has absorbed heat from the battery cells 20A, 20B and vaporized moves vertically upward and is cooled and condensed by the refrigerant 32a in the refrigerant flow passage 30a. The condensed refrigerant 32a spreads widely throughout the porous body 52 due to the capillary phenomenon of the porous body 52. ​​Heat exchange occurs between the refrigerant 32a contained in the porous body 52 and the battery cells 20A, 20B via the heat transfer layer 51, and the refrigerant 32a vaporizes again.

[0043] In the state of the battery cells 20A, 20B shown in FIG. 6, if the battery cell 20A or the battery cell 20B ignites, the temperature in the storage section 10a rises rapidly. When the temperature rises rapidly, the liquid of the medium 15a cooled by the refrigerant 32a does not spread over the entire surface of the battery cells 20A, 20B. That is, dry-out occurs, in which the battery cells 20A, 20B cannot be cooled by vapor heat transport using the latent heat of evaporation of the medium 15a. When dry-out occurs, heat is transferred from the ignited battery cell to the adjacent battery cell due to radiant heat between the heat transfer layers 51 formed on the surfaces of the adjacent battery cells 20A, 20B. However, in the second embodiment, the heat transfer layer 51 is quickly cooled because it is connected to the refrigerant flow path 30a, and heat transfer due to radiant heat is suppressed.

[0044] Each of the figures from FIG. 7 to FIG. 11 is an explanatory diagram of the spread of fire in the battery cell 20 of the second embodiment. FIG. 7 shows eight battery cells 20A to 20H arranged in the storage section 10a of the second embodiment. As shown in FIG. 7, the temperatures of the eight battery cells 20A to 20H are Ta to Th. In the example shown in FIG. 7 to FIG. 11, when the battery cell 20A located on the most negative side along the X-axis among the eight battery cells 20A to 20H ignites, the evaluation of the spread of fire to the other seven battery cells 20B to 20H is shown. In the example shown in FIG. 7 to FIG. 11, the distance L3 between the two adjacent battery cells 20 shown in FIG. 6 is 4 mm. The distance L2 between the heat transfer layers 51 formed on the surfaces of the two battery cells 20 is 3 mm. The distance L1 between the porous bodies 52 formed on the surfaces of the heat transfer layers 51 of the two battery cells 20 is 2 mm. In other words, the thickness of each of the heat transfer layer 51 and the porous body 52 along the X-axis direction is 0.5 mm, and the thickness of the space formed between adjacent porous bodies 52 through which the medium 15a flows is 2 mm.

[0045] FIG. 8 shows temperature changes Cta-Ctf of the temperatures Ta-Tf (FIG. 7) of the six battery cells 20A-20F when the battery cell 20A catches fire. The temperatures Tg and Th of the two battery cells 20G and 20H barely change, so the temperature changes are omitted in FIG. 8. As shown in FIG. 8, the temperatures Ta-Td of the four battery cells 20A-20D rise to nearly 500°C as time passes. That is, the fire spreads from the ignited battery cell 20A to the three battery cells 20B-20D. On the other hand, the temperature changes Cte and Ctf of the two battery cells 20E and 20F barely change. That is, the fire did not spread from the ignited battery cell 20A to the four battery cells 20E-20H, including the two battery cells 20E and 20F.

[0046] 9 shows the measurement positions of the heat fluxes shown in FIGS. 10 and 11. As shown in FIG. 9, the heat fluxes on the surfaces on the negative X-axis side of each of the eight battery cells 20A-20H are QLa to QLh. The heat fluxes on the surfaces on the positive X-axis side of each of the eight battery cells 20A-20H are QRa to QRh. The heat flux on the wall surface on the negative X-axis side in the accommodation section 10a is QL0, and the heat flux on the wall surface on the positive X-axis side is QR0. The measurement position of the heat flux in the Z-axis direction (vertical direction) is midway between the accommodation section 10a and the battery cells 20A-20H.

[0047] When the heat flux at each position is defined as in Fig. 9, Fig. 10 shows the change in heat flux over time during radiation, and Fig. 11 shows the change in heat flux over time to the cross section of the heat transfer layer 51. In Fig. 10, positive values ​​on the vertical axis represent emission by radiation, and negative values ​​represent absorption by radiation. In Fig. 10, the changes in heat flux corresponding to the heat fluxes QLa-QLe, QRa-QRd, and QL0 are represented by CLa-CLe, CRa-CRd, and CL0, respectively. For example, the change in heat flux CRa (thin solid line) starts at -10,000 W / m 2 Therefore, 10000W / m 2After functioning as a heat flux absorption surface, the battery cells 20E-20H located on the positive side of the X-axis first function as a heat flux radiation surface. In the second embodiment, the four battery cells 20E-20H located on the positive side of the X-axis do not ignite. Therefore, when the heat fluxes QLf-QLh, QRe-QRh of these battery cells 20E-20H and the heat flux QR0 of the housing portion 10a function as a radiation radiation surface, the heat flux is small.

[0048] 11, the changes in heat flux to the heat transfer layer 51 corresponding to the heat fluxes QLa-QLe, QRa-QRd, and QL0 are represented by CLa-CLe, CRa-CRd, and CL0, respectively. The changes in heat flux CLa-CLe, CRa-CRd, and CL0 shown in FIG. 6 (W / m 2 ) or more. That is, each of the heat fluxes QLa to QLe, QRa to QRd, and QL0 radiates more heat to the heat transfer layer 51 than to the battery cells 20. Therefore, the spread of fire to the four battery cells 20E to 20H among the eight battery cells 20A to 20H is suppressed.

[0049] FIG. 12 is an explanatory diagram of temperature changes Cta-Cth of temperatures Ta-Th of eight battery cells 20A-20H in a secondary battery system 100x not including a second thermal expansion valve 82. In contrast to the secondary battery system 100a of the second embodiment, in the secondary battery system 100x not including the second thermal expansion valve 82, the refrigerant 32a expands using the first thermal expansion valve 81 even when the battery cell 20A ignites. FIG. 12 shows temperature changes Cta-Cth of the eight battery cells 20A-20H corresponding to FIG. 8 in the case of the secondary battery system 100x. As shown by the temperature changes Cta-Cth in FIG. 12, the temperatures of all of the eight battery cells 20A-20H rise to 500°C or higher within 30 minutes. That is, all of the eight battery cells 20A-20H ignite within 30 minutes.

[0050] 13 is an explanatory diagram of the changes CLa-CLh, CRa-CRh, CL0, and CR0 of the heat fluxes QLa-QLh, QRa-QRh, QL0, and QR0 of the eight batteries 20A-20H in the secondary battery system 100x that does not include the second thermal expansion valve 82. As shown by the changes in heat fluxes CLa-CLh, CRa-CRh, CL0, and CR0 in FIG. 13, all of the eight battery cells 20A-20H have ignited, so the changes in all of the heat fluxes are large. Thus, compared to the secondary battery system 100x that does not include the second thermal expansion valve 82, the secondary battery system 100a of the second embodiment that includes the second thermal expansion valve 82 suppresses the spread of fire in the four battery cells 20E-20H.

[0051] As described above, the medium 15a in the second embodiment is a fluorocarbon-based medium with a low boiling point. The control unit 40 controls the temperature of the medium 15a by controlling the temperature of the refrigerant 32a supplied to the refrigerant flow path 30a in the storage unit 10a using the temperature detected by the temperature sensor S1. The control unit 40 controls the temperature of the medium 15a, and adjusts the temperature of the plurality of battery cells 20 using the heat of evaporation of the medium 15a and changes the vapor pressure of the medium 15a by controlling the temperature of the medium 15a. In this embodiment, during charging and discharging when the battery cells 20 are not ignited, the temperature and boiling point during charging and discharging are adjusted to efficiently cool the battery cells 20 by utilizing the latent heat of evaporation of the medium 15a, which is a fluorocarbon-based medium. In addition, ignition of the battery cell 20 is detected by the temperature of the battery cell 20 acquired by the temperature sensor S1. When the battery cell 20 ignites, the temperature of the medium 15a is further lowered than that during charging and discharging of the battery cell 20, thereby cooling the ignited battery cell 20 and suppressing the spread of fire between the battery cells 20.

[0052] In addition, the first thermal expansion valve 81 and the second thermal expansion valve 82 of the second embodiment expand the refrigerant 32a flowing through the external flow path 35 by the pressure difference between the upstream side and the downstream side of the valve. The second thermal expansion valve 82 has a larger pressure difference than the first thermal expansion valve 81. When the temperature detected by the temperature sensor S1 is less than the threshold value of 80°C, the control unit 40 connects the external flow path 35 to the first thermal expansion valve 81. In this case, the control unit 40 supplies the refrigerant 32a cooled to 20°C through the first thermal expansion valve 81 to the refrigerant flow path 30a in the storage unit 10a. When the temperature detected by the temperature sensor S1 reaches 80°C, the control unit 40 supplies the refrigerant 32a to the refrigerant flow path 30a in the storage unit 10a through the second thermal expansion valve 82 instead of the first thermal expansion valve 81. In this embodiment, the refrigerant 32a is supplied to the refrigerant flow path 30a in the storage unit 10a through the first thermal expansion valve 81 during charging and discharging of the battery cell 20. When the battery cell 20 ignites, the refrigerant 32a is supplied to the refrigerant flow path 30a in the storage section 10a via the second thermal expansion valve 82. As a result, when the battery cell 20 ignites, the refrigerant 32a, which has expanded further due to the pressure difference and has a lower temperature than the first thermal expansion valve 81, is supplied to the refrigerant flow path 30a via the second thermal expansion valve 82. As a result, the storage section 10a that contains the ignited battery cell 20 is supplied with refrigerant 32a at a lower temperature than when the battery cell 20 is not ignited, and the ignited battery cell 20 is cooled.

[0053] The heat transfer member 50a of the second embodiment includes a heat transfer layer 51 formed in direct contact with the surfaces of the battery cells 20A and 20B, and a porous body 52 formed of a porous material on the surface of the heat transfer layer 51. The heat transfer layer 51 is formed of a metal with high thermal conductivity. The porous body 52 is formed on the surface of the heat transfer layer 51 formed on the surfaces of the battery cells 20A and 20B without being in direct contact with the battery cells 20A and 20B. In this embodiment, the liquid medium 15a cooled by the refrigerant 32a flowing through the refrigerant flow path 30a spreads quickly throughout the porous body 52 due to the capillary phenomenon caused by the porous body 52 connected to the refrigerant flow path 30a. The liquid medium 15a in the porous body 52 exchanges heat with the battery cells 20 through the heat transfer layer 51 in contact with the porous body 52. The medium 15a, which has changed from liquid to gas due to heat exchange, moves above the battery cell 20 in which the refrigerant flow path 30a is arranged, is cooled and changes to liquid, and cools the battery cell 20 again. That is, in this embodiment, the battery cell 20 is quickly cooled by the vapor heat transport of the medium 15a using the capillary phenomenon of the porous body 52. ​​On the other hand, if the battery cell 20 ignites and is at a high temperature, the medium 15a cannot condense in time and dry-out occurs around the ignited battery cell 20. When dry-out occurs, heat is transferred from the ignited battery cell 20 to the adjacent battery cell 20 by thermal radiation from the heat transfer layer 51. In this embodiment, the heat transfer layer 51 is connected to the refrigerant flow path 30a, so that the battery cell 20 is quickly cooled and heat transfer between the battery cells 20 due to thermal radiation is suppressed.

[0054] <Third embodiment> 14 and 15 are schematic block diagrams of a secondary battery system 100b of the third embodiment. The secondary battery system 100b of the third embodiment is different from the secondary battery system 100a of the second embodiment in that it includes a pressure regulating valve 90a instead of the low-pressure pressure regulating valve 90, and does not include the second thermal expansion valve 82, the control unit 40, and the temperature sensor S1.

[0055] 14 and 15, a pressure regulating valve 90a of the third embodiment includes a first pressure regulating valve 91 that releases the pressure in the accommodation portion 10, and a second pressure regulating valve 92 that is connected in series between the accommodation portion 10a and the first pressure regulating valve 91. The first pressure regulating valve 91 opens when the pressure in the accommodation portion 10a reaches a first pressure value. Once the first thermal expansion valve 81 opens, it maintains the open state thereafter. The second pressure regulating valve 92 is a valve that opens when the pressure is equal to or greater than a second pressure value that is smaller than the first pressure value and larger than atmospheric pressure, and closes when the pressure is less than the second pressure value.

[0056] In the third embodiment, the withstand pressure of the container in the storage section 10a is set to 1.5 MPa. In response to this, the first pressure value at which the first pressure regulating valve 91 opens is set to 1.2 MPa. Also, the second pressure value at which the second pressure regulating valve 92 opens is set to 0.1 MPa. The first pressure value and the second pressure value are gauge pressures. In the third embodiment, during charging / discharging when none of the battery cells 20 in the storage section 10a have ignited (FIG. 14), the pressure of the medium 15a in the storage section 10a is set to 0.8 MPa. In this case, as shown in FIG. 14, the first pressure regulating valve 91 is closed and the second pressure regulating valve 92 is open.

[0057] When the battery cells are charged or discharged, if one of the battery cells 20 ignites and the high pressure of the battery cell 20A is released into the storage section 10a by opening the safety valve 21A (FIG. 1) as shown in Fig. 15, the pressure inside the storage section 10a increases. When the increased pressure reaches the first pressure value of 1.2 MPa, the first pressure adjustment valve 91 opens in addition to the second pressure adjustment valve 92. This maintains the pressure inside the storage section 10a at 1.2 MPa or less.

[0058] After the first pressure regulating valve 91 opens, when the ignition of the battery cell 20A and the spread of fire in the other battery cells 20 subside and the pressure inside the storage section 10a drops to 0.1 MPa, the second pressure regulating valve 92 closes, as shown in Fig. 15. This prevents oxygen contained in the air from flowing into the storage section 10a.

[0059] As described above, the pressure regulating valve 90a of the secondary battery system 100b of the third embodiment includes the first pressure regulating valve 91 that releases the pressure in the storage unit 10, and the second pressure regulating valve 92 that is connected in series between the storage unit 10a and the first pressure regulating valve 91. The first pressure regulating valve 91 opens when the pressure in the storage unit 10a reaches a first pressure value. Once the first thermal expansion valve 81 opens, it maintains the open state thereafter. The second pressure regulating valve 92 opens when the pressure is equal to or greater than a second pressure value that is smaller than the first pressure value and greater than atmospheric pressure, and closes when the pressure is less than the second pressure value. In this embodiment, when the battery cell 20 is charging or discharging without ignition, the medium 15a in the storage unit 10a cools the battery cell 20 at a pressure equal to or greater than the second pressure value and less than the first pressure value. In this case, the second pressure regulating valve 92 opens and the first pressure regulating valve 91 closes, so that the medium 15a in the storage unit 10a is not released to the atmosphere. On the other hand, when the battery cell 20 ignites and the pressure in the storage section 10a changes to the first pressure value or more, the first pressure regulating valve 91 opens in addition to the second pressure regulating valve 92. In this case, the medium 15a in the storage section 10a is released to the atmosphere, and the pressure in the storage section 10a decreases. As a result, damage to the containers such as the storage section 10a due to the increase in pressure in the storage section 10a can be suppressed. In addition, if the pressure in the storage section 10a decreases to less than the second pressure value after the first pressure regulating valve 91 opens, the second pressure regulating valve 92 closes. Since the second pressure value is set higher than the atmospheric pressure, air containing oxygen does not flow from the atmosphere into the storage section 10a even if the pressure in the storage section 10a decreases. That is, in this embodiment, the pressure increase when the battery cell 20 ignites is suppressed, so that damage to the containers such as the storage section 10a is suppressed, and the progression of the ignition due to the flow of oxygen from the atmosphere into the storage section 10a is suppressed.

[0060] <Fourth embodiment> Fig. 16 is a schematic block diagram of a secondary battery system 100d of the fourth embodiment. As shown in Fig. 16, the secondary battery system 100d of the fourth embodiment is a system that includes the pressure regulator valve 90a of the third embodiment instead of the low-pressure regulator valve 90 of the secondary battery system 100a of the second embodiment. Therefore, in the fourth embodiment, when the battery cell 20 catches fire, the medium 15a whose temperature is lower than that during charging and discharging is supplied into the storage section 10a as in the second embodiment. This further cools the battery cell 20, and the spread of fire between the battery cells 20 is suppressed.

[0061] Furthermore, in the fourth embodiment, when the battery cell 20 ignites, the first pressure regulating valve opens in addition to the second pressure regulating valve 92 as in the third embodiment. As a result, the medium 15a in the storage section 10a is discharged to the atmosphere, and the pressure in the storage section 10a decreases. As the pressure in the storage section 10a decreases, the electrolyte component discharged from the ignited battery cell 20 into the storage section 10a does not vaporize but remains in the storage section 10a as a liquid. As a result, in the secondary battery system 100d of the fourth embodiment, only one battery cell 20 ignites, and the spread of fire to the other battery cells is suppressed, compared to the second embodiment in which the four battery cells 20A to 20D shown in FIG. 8 ignite. That is, in the fourth embodiment, the spread of fire to the battery cells 20 is further suppressed compared to the second embodiment.

[0062] <Fifth embodiment> Fig. 17 is a schematic block diagram of a secondary battery system 100c of the fifth embodiment. The secondary battery system 100c of the fifth embodiment differs from the secondary battery system 100a of the second embodiment in that it further includes a tank TK that stores antifreeze solution, a pump P1 for circulating the antifreeze solution, and on-off valves 93 and 94. Fig. 17 shows the state of the second embodiment after the state shown in Fig. 6 in which the low-pressure regulating valve 90 is opened after the battery cell 20 in the storage section 10a ignites.

[0063] The antifreeze stored in the tank TK has electrical insulation properties. For example, an antifreeze with an electrical insulation property has a volume resistivity of 1.0×10 13(Ω·m) or more. On-off valves 93, 94 open and close the flow path connecting the tank TK and the inside of the storage unit 10a, as shown in Fig. 17, in response to a control signal from the control unit 40c. When each of the on-off valves 93, 94 is opened and the tank TK and the inside of the storage unit 10a are connected, the pump P1 circulates the antifreeze liquid between the tank TK and the inside of the storage unit 10a.

[0064] As in the second embodiment, when the temperature detected by the temperature sensor S1 changes from less than 80° C. (second temperature) to 80° C. or higher, the control unit 40c opens the low-pressure regulating valve 90 to release the medium 15a in the storage unit 10a to the atmosphere. Thereafter, as shown in FIG. 17, the control unit 40c closes the low-pressure regulating valve 90, opens the on-off valves 93 and 94, and operates the pump P1 to supply antifreeze liquid from the tank TK into the storage unit 10a. When the storage unit 10a is filled with antifreeze liquid to a predetermined amount or more, the control unit 40c stops the operation of the pump P1 and closes the on-off valves 93 and 94.

[0065] 18 is a schematic diagram of the accommodation unit 10a removed from the secondary battery system 100c. When the accommodation unit 10a is filled with antifreeze, the accommodation unit 10a can be removed. The removed accommodation unit 10a is transported to a destruction processing site for safety reasons such as preventing re-ignition.

[0066] Fig. 19 is a schematic diagram of the accommodation unit 10a connected to a cooling circulation system SY different from the secondary battery system 100c. The accommodation unit 10a during transportation is connected to the cooling circulation system SY shown in Fig. 19, for example, and heat exchange is performed to cool the antifreeze liquid in the accommodation unit 10a. As shown in Fig. 19, the cooling circulation system SY includes a heat exchanger 75 capable of exchanging heat with the antifreeze liquid and a pump P2 that circulates the antifreeze liquid. After the interior of the accommodation unit 10a is connected to the flow path of the cooling circulation system SY, the opening and closing valves 93 and 94 are opened and the pump P2 is operated, and the antifreeze liquid is cooled by the heat exchanger 75.

[0067] As described above, the secondary battery system 100c of the fifth embodiment includes a tank TK that stores an antifreeze liquid having electrical insulation. When the temperature detected by the temperature sensor S1 changes from less than 80°C to 80°C or higher, the control unit 40c opens the low-pressure regulating valve 90 to release the medium 15a in the storage unit 10a to the atmosphere. After that, as shown in FIG. 17, the control unit 40c closes the low-pressure regulating valve 90, opens the on-off valves 93 and 94, and operates the pump P1 to supply antifreeze liquid from the tank TK to the storage unit 10a. In this embodiment, when the battery cell 20 changes from a non-ignited state to an ignited state, the storage unit 10a is filled with the supplied antifreeze liquid. By covering the battery cell 20 with antifreeze liquid, contact between the ignited battery cell 20 and oxygen is suppressed, and the temperature of the battery cell 20 is managed by controlling the temperature of the antifreeze liquid. In particular, if there is a battery cell 20 that has not completely combusted, re-ignition of the incompletely combusted battery cell 20 after several hours or days is suppressed by filling the storage section 10a with antifreeze.

[0068] <Modifications of the embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the present invention, for example, the following modifications are possible: In the above-described embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware.

[0069] <Variation 1> In each of the first to fifth embodiments, an example of the secondary battery system 100, 100a, 100b, 100c, and 100d has been described. However, the secondary battery system can be modified as long as the battery cells are accommodated in the accommodation section, the accommodation section is filled with a medium that does not contain oxygen, and a safety valve that releases pressure in the battery cells is disposed in a position facing the cooling section. In the first embodiment, the refrigerant flow path 30 in which the refrigerant 32 flows has been described as an example of a cooling section that cools the battery cells 20 via the medium 15. However, the cooling section disposed in the accommodation section 10 may be a heat sink formed only of a metal material. In this case, the heat sink may dissipate heat by a condenser 70 or the like connected outside the accommodation section 10. As shown in FIG. 3, in the second embodiment, the battery cells 20 are cooled by a refrigeration cycle using the refrigerant 32a, but the battery cells 20 may be cooled by a system in which a liquid circulation system using antifreeze is inserted between the refrigeration cycle and the battery cells 20.

[0070] The medium filled in the storage section 10 may be, for example, nitrogen or the like, other than a fluorocarbon-based medium. For example, in the second embodiment shown in Fig. 6, a heat insulating member having heat insulating properties may be disposed in a portion between the opposing porous bodies 52. The storage section 10 and the battery cell 20 may have a shape other than a rectangular parallelepiped. Instead of the battery cell 20, a battery in which a plurality of battery cells are stacked may be used.

[0071] The position where the refrigerant flow path 30 is formed in the storage section 10 may be other than vertically above the battery cell 20, and may be, for example, vertically below the battery cell 20. When the battery cell 20 is cooled by vapor heat transport using the latent heat of evaporation that utilizes the low boiling point of a fluorocarbon-based medium, as in the second embodiment, it is preferable that the refrigerant flow path 30a is disposed vertically above the battery cell. Note that the vertical direction and the like defined in the orthogonal coordinate system CS are a coordinate system defined to explain the secondary battery system 100 and the like shown in FIG. 1, and these directions may be rotated as appropriate.

[0072] The predetermined pressure value at which the safety valve 21A opens, the temperature of the battery cell 20 at which the control unit 40 switches the connection between the first thermal expansion valve 81 and the second thermal expansion valve 82 in the second embodiment, the pressure value at which the low pressure regulating valve 90 opens, and the first pressure value at which the first pressure regulating valve 91 opens and the second pressure value at which the second pressure regulating valve 92 opens and closes in the third embodiment can be modified according to the specifications of the secondary battery system 100, the battery cell 20, and the like. For example, in the second embodiment, when the temperature of the battery cell 20 is 80°C, it is determined that the battery cell 20 has ignited, and the refrigerant 32a expands by the second thermal expansion valve 82. However, for example, when the temperature of the battery cell 20 reaches 100°C, the connection may be switched from the first thermal expansion valve 81 to the second thermal expansion valve 82. In addition, the secondary battery system of the modified example may include three or more thermal expansion valves that expand the refrigerant 32a by different pressure differences. In this case, the connection of three or more thermal expansion valves may be switched according to the detected temperature of the temperature sensor S1 at two or more stages.

[0073] Although the present aspect has been described above based on the embodiment and modified examples, the above-mentioned embodiment of the aspect is intended to facilitate understanding of the present aspect and does not limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents are included in the present aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0074] The present invention can also be realized in the following forms. [Application example 1] A secondary battery system, A secondary battery; a storage section that stores the secondary battery and is filled with an oxygen-free medium; a cooling unit that is disposed inside the housing and cools the secondary battery via the medium; Equipped with the secondary battery has a safety valve that releases pressure inside the secondary battery when the pressure inside the secondary battery reaches a predetermined pressure value; The safety valve is disposed at a position facing the cooling unit with the medium interposed therebetween. [Application example 2] The secondary battery system according to Application Example 1, A secondary battery system, wherein the distance between the safety valve and the cooling section is set to be equal to or less than a quenching distance. [Application example 3] The secondary battery system according to Application Example 1 or 2, further comprising: a temperature acquisition unit that acquires a battery temperature, which is a temperature of the secondary battery; A control unit that controls the temperature and pressure of the medium using the battery temperature; Equipped with The medium is a fluorocarbon-based medium, the cooling unit is disposed vertically above the secondary battery, The control unit controls the temperature of the fluorocarbon-based medium to adjust the temperature of the secondary battery using heat of evaporation of the fluorocarbon-based medium and to change the vapor pressure of the fluorocarbon-based medium. [Application example 4] The secondary battery system according to any one of Application Examples 1 to 3, The cooling unit has a refrigerant flow path through which a refrigerant flows, The secondary battery system further comprises: a first thermal expansion valve for expanding the refrigerant by a pressure difference between an upstream side and a downstream side of the first thermal expansion valve; a second thermal expansion valve that expands the refrigerant by a pressure difference between its upstream side and downstream side, the pressure difference being greater than the pressure difference of the first thermal expansion valve; Equipped with The control unit is supplying the refrigerant to the secondary battery via the first thermal expansion valve when the battery temperature is lower than a first temperature; the refrigerant is supplied to the secondary battery via the second thermal expansion valve when the battery temperature is equal to or higher than the first temperature. [Application example 5] The secondary battery system according to any one of Application Examples 1 to 4, further comprising: a heat transfer layer made of metal, connected to a surface of the secondary battery and connected to the refrigerant flow path; a porous body connected to the secondary battery via the heat transfer layer and formed of a porous material; The secondary battery system includes: [Application Example 6] The secondary battery system according to any one of Application Examples 1 to 5, further comprising: A tank storing an antifreeze liquid having electrical insulation properties; an on-off valve that opens and closes the connection between the storage unit and the outside; Equipped with The control unit is When the battery temperature changes from less than a second temperature to equal to or greater than the second temperature, the fluorocarbon-based medium is released from inside the storage portion by opening the on-off valve; a secondary battery system, wherein an antifreeze solution is supplied from the tank to the inside of the storage portion after the fluorocarbon-based medium is released. [Application Example 7] The secondary battery system according to any one of Application Examples 1 to 6, further comprising: A first pressure regulating valve that releases pressure inside the storage portion; a second pressure regulating valve connected in series between the accommodation portion and the first pressure regulating valve; Equipped with the first pressure regulating valve opens when the pressure inside the accommodation portion reaches a first pressure value and maintains the open state; The second pressure regulating valve opens when the pressure is equal to or greater than a second pressure value that is smaller than the first pressure value and greater than atmospheric pressure, and closes when the pressure is less than the second pressure value. [Explanation of symbols]

[0075] 10, 10a…Housing section 15,15a…medium 20, 20A~20H…Battery cell (secondary battery) 21A, 21B…Safety valve 22...Electrolyte component 30, 30a... Coolant flow path 31…tube wall 32, 32a…Refrigerant 35…External flow path 40, 40c...Control section 50, 50a...Heat transfer member 51...Heat transfer layer 52...Porous body 60…Compressor 70…Condenser 75...Heat exchanger 81…First thermal expansion valve 82…Second thermal expansion valve 90...Low pressure regulator 90a…Pressure adjusting valve 91…First pressure regulating valve 92…Second pressure regulating valve 93...Shut-off valve 100, 100a, 100b, 100c, 100x... Secondary battery system CS...Cartesian coordinate system P1, P2...Pump S1: Temperature sensor (temperature acquisition section) SY…Cooling circulation system TK…Tank

Claims

1. A secondary battery system, A secondary battery; a storage section that stores the secondary battery and is filled with an oxygen-free medium; a cooling unit that is disposed inside the housing and cools the secondary battery via the medium; Equipped with the secondary battery has a safety valve that releases pressure inside the secondary battery when the pressure inside the secondary battery reaches a predetermined pressure value; The safety valve is disposed at a position facing the cooling unit with the medium interposed therebetween.

2. The secondary battery system according to claim 1 , A secondary battery system, wherein the distance between the safety valve and the cooling section is set to be equal to or less than a quenching distance.

3. The secondary battery system according to claim 1 , further comprising: a temperature acquisition unit that acquires a battery temperature, which is a temperature of the secondary battery; A control unit that controls the temperature and pressure of the medium using the battery temperature; Equipped with The medium is a fluorocarbon-based medium, the cooling unit is disposed vertically above the secondary battery, The control unit controls the temperature of the fluorocarbon-based medium to adjust the temperature of the secondary battery using heat of evaporation of the fluorocarbon-based medium and to change the vapor pressure of the fluorocarbon-based medium.

4. The secondary battery system according to claim 3, The cooling unit has a refrigerant flow path through which a refrigerant flows, The secondary battery system further includes: a first thermal expansion valve for expanding the refrigerant by a pressure difference between an upstream side and a downstream side of the first thermal expansion valve; a second thermal expansion valve that expands the refrigerant by a pressure difference between its upstream side and downstream side, the pressure difference being greater than the pressure difference of the first thermal expansion valve; Equipped with The control unit is supplying the refrigerant to the secondary battery via the first thermal expansion valve when the battery temperature is lower than a first temperature; the refrigerant is supplied to the secondary battery via the second thermal expansion valve when the battery temperature is equal to or higher than the first temperature.

5. The secondary battery system according to claim 4, further comprising: a heat transfer layer made of metal, connected to a surface of the secondary battery and connected to the refrigerant flow path; a porous body connected to the secondary battery via the heat transfer layer and formed of a porous material; The secondary battery system includes:

6. The secondary battery system according to claim 3, further comprising: A tank storing an antifreeze liquid having electrical insulation properties; an on-off valve that opens and closes the connection between the storage unit and the outside; Equipped with The control unit is When the battery temperature changes from less than a second temperature to equal to or greater than the second temperature, the opening / closing valve is opened to release the fluorocarbon-based medium from inside the storage portion; a secondary battery system, wherein an antifreeze solution is supplied from the tank to the inside of the storage portion after the fluorocarbon-based medium is released.

7. The secondary battery system according to any one of claims 1 to 6, further comprising: A first pressure regulating valve that releases pressure inside the storage portion; a second pressure regulating valve connected in series between the accommodation portion and the first pressure regulating valve; Equipped with the first pressure regulating valve opens when the pressure inside the accommodation portion reaches a first pressure value and maintains the open state; The second pressure regulating valve opens when the pressure is equal to or greater than a second pressure value that is smaller than the first pressure value and greater than atmospheric pressure, and closes when the pressure is less than the second pressure value.

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